Born to a wealthy Iraqi family, Shamoon emigrated to Iran during late 1940s when the situation for Jews in Iraq worsened. At 18 he traveled to Israel alone, served in the army and then returned to Iran, where he remained until the overthrow of the Shah. The Shamoon family were traders, importing low cost iron to Iran then selling it to other countries. Following the Iranian revolution, Shamoon and his wife emigrated to England. Some years later Sami managed to retrieve some of the family's assets, which had been nationalized in Iran. He bought a 4% stake in Teva Pharmaceuticals during the 1980s, and a decade later he snapped up bankrupt orchard company Yachin-Hakal. Shamoon also holds 21% of Gaon Holdings, which recently declared its intention to go public.